Hello, Marton! Thanks for the questions :) The sources are not available yet, but there's nothing secret about it and I'm going to release it.
It's MQTT-based app, where you could press and hold the screen to record your audio. When you release the screen, it will be sent and played automatically on every launched app (including yours as echo).
I thought it would be nice to provide some live voice channel for new year greetings for sailors, but not sure is it good idea and implementation or not :)